Organic batteries are electrochemical cells which use an organic redox-active compound as active electrode material for storing electrical charge. These secondary batteries are notable for their exceptional properties, such as fast chargeability, long lifetime, low weight, high flexibility and ease of processibility. A multitude of different organic polymeric structures are already known as active electrode materials for charge storage. For instance, the following publications describe polymers comprising organic nitroxide radicals as active units for charge storage: WO 2012/133202 A1, WO 2012/133204 A1, WO 2012/120929 A1, WO 2012/153866 A1, WO 2012/153865 A1, JP 2012-221574 A, JP 2012-221575 A, JP 2012-219109 A, JP 2012-079639 A, WO 2012/029556 A1, WO 2012/153865 A1, JP 2011-252106 A, JP 2011-074317 A, JP 2011-165433 A, WO 2011/034117 A1, WO 2010/140512 A1, WO 2010/104002 A1, JP 2010-238403 A, JP 2010-163551 A, JP 2010-114042 A, WO 2010/002002 A1, WO 2009/038125 A1, JP 2009-298873 A, WO 2004/077593 A1, WO 2009/145225 A1, JP 2009-238612 A, JP 2009-230951 A, JP 2009-205918 A, JP 2008-234909 A, JP 2008-218326 A, WO 2008/099557 A1, WO 2007/141913 A1, US 2002/0041995 A1, EP 1 128 453 A2, A, Vlad, J. Rolland, G. Hauffman, B. Ernould, J. F. Gohy, ChemSusChem 2015, 8, 1692-1696. US 2002/0041995 A1 and JP 2002-117852 A describe examples of polymeric compounds having organic phenoxyl radicals or galvinoxyl radicals.
Other known active units for charge storage are polymeric compounds having quinones (JP 2009-217992 A, WO 2013/099567 A1, WO 2011/068217 A1), having diones (JP 2010-212152 A), and having dicyanodiirnines (JP 2012-190545 A, JP 2010-55923 A).
Other publications describe the use of dialkoxybenzene derivatives as “redox-shuttle” additives for Li ion batteries (WO 2011/149970 A2) and polymers comprising dialkoxybenzene as electrical charge storage means (P. Nesvadba, L. B. Folger, P. Maire, P. Novak, Synth.Met. 2011, 161, 259-262; W. Weng, Z. C. Zhang, A. Abouimrane, P. C. Redfern, L. A. Curtiss, K. Amine, Adv. Funct. Mater. 2012, 22, 4485-4492).
In addition, there exists a further substance class of polymers comprising thianthrene units. These have been described for various technical fields, for example as networks for gas storage and materials having high refractive index. Corresponding publications/patents are, for example: P. C. Bizzarri, C. Dellacasa, Mol. Cryst. Liq. Cryst. 1985, 118, 245-248; L. C. Dunn, W. T. Ford, N. Hilal, P. S. Vijayakumar, H. A. Pohl, J. Polym, Sci. Pol. Phys. 1984, 22, 2243-2260; T. Yamamoto, T. Okuda, J. Electroanal. Chem. 1999, 460, 242-244; Y. Suzuki, K. Murakami, S. Ando, T. Higashihara, M. Ueda, J. Mater. Chem. 2011, 21, 15727-15731; WO 2009/106198 A1, DE 19733882 A1, JP 2012-177057 A, DE 3520102 A1, JP 2012-177057 A, DE 19532574 A1, DE 19733882 C2, WO 2012/172177 A1. In most of the thianthrene-containing polymers described in the prior art, the thianthrene structure is in the main chain. Other publications describe polymers which bear the thianthrene unit in the side chain. Most of these publications discuss the high refractive indices of these polymers (EP 0 320 954 A2, WO 2012/172177 A1 US 2011/0183263 A1, H. Hopif, H. Gutenberg, Makromolekul. Chem. 1963, 60, 129-138).
Non-polymeric thianthrene derivatives have also been used as additives for lithium ion batteries in order to prevent overcharging of the lithium ion battery (U.S. Pat. No. 5,858,573 A, WO 2010/096404 A2, EP 0 825 663 A2, S. A. Odom, S. Ergun, P. P. Poudel, S. R. Parkin, Energ. Environ. Sci. 2014, 7, 760-767) or in order to increase the thermal stability thereof (JP 2001-307738 A). In addition, the thianthrene radical has been used as a non-polymeric compound for charge storage (US 2002/0041995 A1).
The publication by M. E. Speer, M. Kolek, J. J. Jassoy, J. Heine, M. Winter, P. M. Bieker, B. Esser, Chem. Commun. 2015, 51, 15261-15264 (abbreviated hereinafter to “Speer et al.”) describes polymers which have thianthrene units in the side chain and norbornenyl units in the main chain and find use as active materials in electrical working memory. These thianthrene-containing polymers feature a higher redox potential compared to other organic cathode materials, since they permit a higher voltage, for example, compared to the nitroxide-based batteries.
However, it has been observed that the thianthrene-containing polymers described by Speer et at. have low cycling stability and a low capacity. This automatically leads to a low specific energy.
The problem addressed by the present invention was therefore that of providing polymers which have a higher capacity and higher cycling stability compared to the thianthrene-containing polymers described in the prior art. Thianthrene-containing polymers which solve the aforementioned problem have now been developed.